There has been known a tandem type electrophotographic color printer. The printer includes an image forming unit that is mounted in and dismounted from a main casing when a cover is open. Typically, four photosensitive drums and four developing rollers are mounted on the image forming unit. The four developing rollers are in slidable contact with the four photosensitive drums respectively. With the four photosensitive drums and four developing rollers, yellow, cyan, magenta and black toner images are formed individually on the four photosensitive drums.
The image forming unit further includes a belt unit disposed below the image forming unit. The belt unit is configured from a pair of support rollers disposed in spaced-apart relation with each other, and an endless conveyor belt circularly movably supported between the support rollers. The belt unit is provided for conveying recording sheets of paper. In the structure of the color printer described above, the image forming unit disposed in the main casing bothers dismounting the belt unit from the main casing. That is, the belt unit cannot be dismounted from the main casing until the image forming unit is dismounted therefrom. An opening is formed in the main casing through which the image forming unit and the belt unit is mounted or dismounted.
In the color printer described above, an electrostatic latent image is formed on each of the photosensitive drums and is developed by the relevant color toner supplied by the associated developing roller. The toner images formed on the respective photosensitive drums are sequentially transferred on a recording paper to overlap one on the other as the recording paper is conveyed by the conveyor belt, thereby forming a color image on the recording paper.
Another type of color printer employs a belt unit. This belt unit is, however, not used for conveying the recording paper but used as an intermediate transfer belt. The toner images formed on the photosensitive drums are once transferred on the intermediate transfer belt and then transferred on a recording paper from the intermediate transfer belt. An intermediate transfer roller is disposed at the side of the intermediate transfer belt to abut the surface of the intermediate transfer belt.